code: def maemetric_np(y_pred, y):
      return np.mean(np.abs(flatten(y_pred) - flatten(y)))
  
file_path: MONAI/tests/test_handler_regression_metrics.py
imports: from __future__ import annotations
  import unittest
  from functools import partial
  import numpy
  import torch
  from ignite.engine import Engine
  from monai.handlers import MeanAbsoluteError, MeanSquaredError, PeakSignalToNoiseRatio, RootMeanSquaredError
  from monai.utils import set_determinism
label_desc: Use image node_id 3 for calling a global function with example usage: maemetric_np(y_pred, y) and returns: np